Supplemental slides – E and Z isomers.pptx - Supplemental...

Supplemental slides – E and Z
isomers
•
Di-, tri-, or tetrasubstituted alkenes may be assigned E or Z designation – i.e. any
alkene that has two different groups on each carbon of the alkene
•
These cannot be assigned!
•
These can be assigned E or Z!
2 different
groups
2 different
groups
•
As long as both sides (on either side of the
dotted line) have different groups on each
carbon, E or Z can be determined.

Cahn-Ingold-Prelog (CIP) rules
•
The rules are (deceptively) simple:
• Higher priority = higher atomic number
•
Check priority one bond length away* at a time . Highest priority at any
position the same bond length away wins
•
If there are ties, the most bonds to the higher priority atom wins
•
E.g.: Using CIP rules to assign E or Z
Level 2: the leftmost